Electroacoustical apparatus



July 4, 1939. SAMAL 2,164,756

- ELECTBOAGOUSTICAL APPARATUS Filed March 51, 1938 Ji l/Inn,

Snventor Gttomeg Patented July 4, 1939 UNITED STATES PATENT OFFICE Radio Corporation of of Delaware America, a corporation Application Mac]. 31, 1938, Serial No. 199,322

1 Claim.

This invention relates to electroacoustical apparatus, such as microphones, employing damped acoustic lines, and more particularly to a method of and means for placing damping material with- 5 in said lines and securing same in place therein.

Considerable difficulty is frequently experienced in placing suitable damping material within acoustic lines, such as long pipes or tubes employed in connection with microphones. In some 10 cases, even where little difllculty is experienced in this connection, it often happens that the acoustic damping material is disturbed from its intended position during handling of the apparatus and movement thereof from place to place. The primary object of my present invention is to provide a simple and accurate method of placing the damping material within and securing the same to the acoustic line. More particularly, it is an'object of my in- 20 vention to provide a novel method of securing within a relatively long acoustic pipe or tube a plurality of tufts of damping material at spaced intervals therealong.

In accordance with my present invention, and

25 in order to overcome the difficulty of placing damping material, such as tufts of felt, at'definitely spaced intervals in the acoustic line, I fasten the tufts by cement or otherwise to a string or other flexible member and thereafter thread :30 the same through the tube or pipe, pulling the string through until the tufts are located in the desired position. The string is then secured at each end to any convenient anchoring means fixed with respect to the pipe, so that the damping 36 material remains where it was originally placed.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claim. The invention itself, however, together with additional objects 40 and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing, in which,

Figure 1 is a view showing the manner in which 43 the tufts may be secured to a string or the like at spaced intervals prior to insertion into the acoustic line, and

Figure 2 is a sectional view of the assembly. Referring more particularly to the drawing, l wherein similar reference characters indicate corresponding parts throughout, I have shown a flexible element I, such as' a string, tape, wire.

or the like, to which a plurality of tufts 3 of felt or other suitable damping material may be secured at spaced points therealong. The string orthe like I may either be tied around the tufts 3 to securely hold them in the desired spaced rela- 5 tion, or the tufts 3 may be cemented or otherwise suitably secured to the flexible element I.

After the string or the like I and the tufts 3 have been assembled, as previously described, one

end of the string I is inserted into one end of an acoustic pipe or line 5 and it is threaded and pulled through the pipe 5, the tufts 3 being large enough to completely fill the pipe 5 in cross section, and the string I being long enough to extend entirely through the pipe 5. For example, the left hand end of the string I may be inserted through the right hand end of the tube 5 and, while the right hand end of the'string I is held outside of the tube or pipe 5, the first named end thereof is pulled through the pipe until it extends through the left hand end thereof. This will locate the tufts 3 in the manner shown in Fig. 2. Thereafter, the two protruding ends Ia and lb of the string I may be secured to suitable anchoring members I which are fixed relative to the pipe 5, and the tufts 3 will thereafter always remain in the position in which they are originally placed.

Although I have shown and described one form ofmy invention, it will be obvious to those skilled 80 in the art that my invention may also be carried out in other ways. For example, in place of a flexible element I, a solid bar or rod may be employed. to which the tufts 3 are suitably secured. Other changes will, no doubt, also readily suggest themselves to those skilled in the. art.

I therefore desire that my invention shall not be limited except insofar as is made necessary by the prior art and by the spirit of the appended claim. 40

I claim as my invention:

The method of fixing a plurality of tufts of damping material within a relatively long acoustic pipe at spaced points therealong which comprises fastening said tufts individually to a string at predetermined points therealong, thereafter threading said string through said pipe whereby to dispose said tufts at said points within said pipe, and finally securing the ends of said string to members which are fixed relative to said pipe.

mm J. SANIAL. 

